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<td ><a href="../qtdoc/index.html">Qt 5.14</a></td><td ><a href="qdoc-index.html">QDoc Manual</a></td><td >Thread Support</td></tr></table><table class="buildversion"><tr>
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<h3><a name="toc">Contents</a></h3>
<ul>
<li class="level1"><a href="#example">Example</a></li>
<li class="level1"><a href="#commands">Commands</a></li>
<li class="level2"><a href="#threadsafe">\threadsafe</a></li>
<li class="level2"><a href="#reentrant">\reentrant</a></li>
<li class="level2"><a href="#nonreentrant">\nonreentrant</a></li>
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<h1 class="title">Thread Support</h1>
<span class="subtitle"></span>
<!-- $$$17-qdoc-commands-thread.html-description -->
<div class="descr"> <a name="details"></a>
<p>The thread support commands are for specifying the level of support for multithreaded programming in a class or function. There are three levels of support: <code>threadsafe</code>, <code>reentrant</code> and <code>nonreentrant</code>.</p>
<p>The default is <code>nonreentrant</code> which means that the associated class or function cannot be called by multiple threads. <code>Reentrant</code> and <code>threadsafe</code> are levels primarily used for classes.</p>
<p><code>Reentrant</code> means that all the functions in the referenced class can be called simultaneously by multiple threads, provided that each invocation of the functions reference unique data. While <code>threadsafe</code> means that all the functions in the referenced class can be called simultaneously by multiple threads even when each invocation references shared data.</p>
<p>When a class is marked <a href="17-qdoc-commands-thread.html#reentrant-command">\reentrant</a> or <a href="17-qdoc-commands-thread.html#threadsafe-command">\threadsafe</a>, functions in that class can be marked <code>nonreentrant</code> using the <a href="17-qdoc-commands-thread.html#nonreentrant-command">\nonreentrant</a> command.</p>
<a name="example"></a>
<h2 id="example">Example</h2>
<a name="reentrant-example"></a><pre class="cpp">

  \beginqdoc
      \<span class="keyword">class</span> <span class="type"><a href="../qtcore/qlocale.html">QLocale</a></span>
      \brief The <span class="type"><a href="../qtcore/qlocale.html">QLocale</a></span> <span class="keyword">class</span> converts between numbers and their
      string representations in various languages<span class="operator">.</span>

      \reentrant
      \ingroup i18n
      \ingroup text

      <span class="type"><a href="../qtcore/qlocale.html">QLocale</a></span> is initialized with a language<span class="operator">/</span>country pair in its
      constructor and offers number<span class="operator">-</span>to<span class="operator">-</span>string and string<span class="operator">-</span>to<span class="operator">-</span>number
      conversion functions similar to those in <span class="type"><a href="../qtcore/qstring.html">QString</a></span><span class="operator">.</span>

      <span class="operator">.</span><span class="operator">.</span><span class="operator">.</span>

      \nonreentrant

      Sets the global <span class="keyword">default</span> locale to \a locale<span class="operator">.</span> These values are
      used when a <span class="type"><a href="../qtcore/qlocale.html">QLocale</a></span> object is constructed with no
      arguments<span class="operator">.</span> If <span class="keyword">this</span> function is <span class="keyword">not</span> called<span class="operator">,</span> the system<span class="char">'s locale
      is used.

      \warning In a multithreaded application, the default locale
      should be set at application startup, before any non-GUI
      threads are created.

      \sa system(), c()
  \endqdoc
  void QLocale::setDefault(const QLocale &amp;locale)
  {
      default_d = locale.d;
  }
  </span>

</pre>
<p>QDoc renders this as:</p>
<blockquote>            <h1><center>QLocale Class Reference</center></h1>
        <p>The <a href="../qtcore/qlocale.html">QLocale</a> class converts between numbers and their string representations in various languages. More..&#x2e;</p>
<pre class="cpp">

  <span class="preprocessor">#include &lt;QLocale&gt;</span>

</pre>
<p><b>Note:</b> All the functions in this class are <a href="17-qdoc-commands-thread.html#reentrant">reentrant</a>, except <a href="../qtcore/qlocale.html#setDefault">setDefault()</a>.</p>
<p>...</p>
            <hr />
            <h2>Member Type Documentation</h2>
        <p>...</p>
            <h3>void QLocale::setDefault ( const QLocale & locale ) </h3>
        <p>Sets the global default locale to locale. These values are used when a <a href="../qtcore/qlocale.html">QLocale</a> object is constructed with no arguments. If this function is not called, the system's locale is used.</p>
<p><b>Warning:</b> In a multithreaded application, the default locale should be set at application startup, before any non-GUI threads are created.</p>
<p><b>Warning:</b> This function is not reentrant.</p>
<p>See also <a href="../qtcore/qlocale.html#system">system()</a> and <a href="../qtcore/qlocale.html#c">c()</a>.</p>
<p>...</p>
</blockquote>
<p>As shown above, QDoc generates a notification when a class is declared reentrant, and lists the exceptions (the declared nonreentrant functions). A link to the general documentation on <a href="17-qdoc-commands-thread.html#reentrant">reentrancy and thread-safety</a> is included. In addition a warning, &quot;<b>Warning</b>: This function is not reentrant.&quot;, is generated in the nonreentrant functions' documentation.</p>
<p>QDoc will generate the same notification and warnings when a class is declared threadsafe.</p>
<p>For more information see the general documentation on <a href="17-qdoc-commands-thread.html#reentrant">reentrancy and thread-safety</a>.</p>
<a name="commands"></a>
<h2 id="commands">Commands</h2>
<a name="threadsafe-command"></a><a name="threadsafe"></a>
<h3 id="threadsafe">\threadsafe</h3>
<p>The \threadsafe command includes a line in the documentation to indicate that the associated class or function is <i>threadsafe</i> and can be called simultaneously by multiple threads, even when separate invocations reference shared data.</p>
<p>The command must stand on its own line.</p>
<p>The documentation generated from this command will be similar to the what is generated for the <a href="17-qdoc-commands-thread.html#reentrant-command">\reentrant</a> command. See the example above in the <a href="17-qdoc-commands-thread.html#reentrant-example">introduction</a>.</p>
<p>See also <a href="17-qdoc-commands-thread.html#reentrant-command">\reentrant</a> and <a href="17-qdoc-commands-thread.html#nonreentrant-command">\nonreentrant</a>.</p>
<a name="reentrant-command"></a><a name="reentrant"></a>
<h3 id="reentrant">\reentrant</h3>
<p>The \reentrant command indicates that the associated class or function can be called simultaneously by multiple threads, provided that each invocation references its own data. See the <a href="17-qdoc-commands-thread.html#reentrant-example">example</a> above.</p>
<p>The command must stand on its own line.</p>
<p>See also <a href="17-qdoc-commands-thread.html#nonreentrant-command">\nonreentrant</a> and <a href="17-qdoc-commands-thread.html#threadsafe-command">\threadsafe</a>.</p>
<a name="nonreentrant-command"></a><a name="nonreentrant"></a>
<h3 id="nonreentrant">\nonreentrant</h3>
<p>The \nonreentrant command indicates that the associated class or function cannot be called by multiple threads. Nonreentrant is the default case.</p>
<p>The command must stand on its own line.</p>
<p>When a class is marked <a href="17-qdoc-commands-thread.html#reentrant-command">\reentrant</a> or <a href="17-qdoc-commands-thread.html#threadsafe-command">\threadsafe</a>, functions in that class can be marked <code>nonreentrant</code> using this command in the <a href="13-qdoc-commands-topics.html#fn-command">\fn</a> comment of the functions to be excluded.</p>
<p>See also <a href="17-qdoc-commands-thread.html#reentrant-command">\reentrant</a> and <a href="17-qdoc-commands-thread.html#threadsafe-command">\threadsafe</a>.</p>
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